DESCRIPTION: The Lung Health Study (LHS), conducted from 1986-1994, demonstrated that smoking intervention program in middle-aged long-term cigarette smokers can result in a highly significant beneficial effect on the rate of FEV1 decline over five years. However, FEV1 is only a surrogate marker for clinical outcomes of respiratory morbidity and mortality. The present study proposes long term post-trial follow-up of former LHS participants to assess the incidence of morbidity and mortality from respiratory and cardiovascular diseases and other causes, as documented by hospital, clinic, and death records. A pulmonary function test 11 to 12 years after entry into the LHS is also proposed to determine long-term effects of the LHS smoking intervention program on lung function. The main objectives of the study are: 1) to determine, using an intent- to-treat analysis, whether the LHS smoking intervention significantly reduces the incidence of clinically important respiratory and cardiovascular disease over a 12- to 15- year period following study enrollment; 2) to determine whether the beneficial effect of the smoking intervention program on measures of lung function persist through 10 to 12 years of follow-up; 3) to estimate the magnitude of the effects of FEV1 and FVC on the risks of cardiovascular and respiratory morbidity and mortality, after controlling for smoking history; 4)to study the role of other factors [gender, airways reactivity, weight gain, and co- morbidities] in determining the rate of decline in pulmonary function and the risks of cardiovascular and respiratory morbidity and mortality; and 5) to determine whether the improvement in lung function and reduction in respiratory symptoms associated with smoking cessation result in improved health-related quality of life (HRQL) and less depression over an extended follow-up period. All ten of the original LHS clinical centers plan to participate. To minimize bias, all surviving participants of the LHS will be invited to participate, giving a potential sample size of 5600.